The above-mentioned electronic and ionic processes are repeated by receiving electrons from the reducer through the latent image centre because it is a deep electron trap. The emulsion film is soaked in a developing solution, namely a reduction chemical. This signal is chemically amplified during the development procedure. The energy level of an aggregate equal to or larger than Ag_4 is sufficiently deep to be “developable”, and the sensitisation centre at this stage is called the “latent image centre”. These electronic and ionic processes are repeated several times to form an aggregate of silver atoms, Ag_n-1 + e − + Ag^+ →Ag_n, deepening its energy level. The sensitisation centre is again positively charged, being ready to trap an electron. The silver ion reacts with the trapped electron and forms a single silver atom (Ag^+ + e −→Ag, ionic process). The sensitisation centre, which traps an electron, is negatively charged therefore, it attracts interstitial silver ions, which are ions migrating in the crystal lattice. ![]() sulphur-and-gold sensitisation), which is positively charged at the initial stage and works as an electron trap. The sensitisation centre is artificially created via chemical sensitisation (e.g. Owing to shallow electron traps of 21–25 meV, the electrons diffuse inside the crystal until they are trapped in one of the sensitisation centres located at the surface of the crystal (electronic process). When a charged particle passes though the crystal, electrons in the valence band are transferred to the conduction band. An AgBr crystal has a band gap of 2.684 eV. The crystal structure of AgBr used for nuclear emulsions is face-centred cubic, and its shape is octahedral, as shown in Fig. The recent nuclear emulsion is made from silver bromide with a small fraction of iodide (AgBr_1-xI_x, x being the fraction of iodide, about a few mol%). Herein, we discuss the detection principle of nuclear emulsions for ionizing particles. The latest knowledge of the general photographic process is described in. This makes emulsion detectors unique as particle detectors. ![]() Each crystal has a typical diameter of 200 nm and works as an independent detection channel, which results in a very high detection channel density of O (10 14) channels/cm 3 in emulsion detectors. In this chapter, we will mainly focus on developments in experimental techniques for particle physics and briefly present a selection of the main experimental results.Ī nuclear emulsion comprises a large number of small silver halide crystals, uniformly dispersed in gelatine. Indeed, a huge potential of emulsion detectors in applied research will be shown in this study. In particular, they are unsurpassed for the topological detection of short-lived particles and for specific applications in neutrino physics and other emerging fields. Although there was a period of decline of the emulsion technique, the interest in the technique has moved into the front line of physics research because of the advances in digital read-out by high-speed automated scanning and the continuous development of emulsion gel design. Emulsions have contributed to outstanding achievements and discoveries in particle physics. ![]() Among all tracking devices used in particle physics, nuclear emulsion particle detectors feature the highest spatial resolution in measuring ionizing particle tracks.
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